DE2037926A1 - Porcelain electrical insulator and processes for its manufacture - Google Patents

Description

The invention relates to porcelain electrical insulators and, more particularly, to crystallite / alumina porcelain electrical insulators with excellent mechanical properties, which are suitable for use at high and ultra-high voltages, and an improved method of making the same.

In porcelain electrical insulators are present three different porcelains used, namely 1 feldspar porcelain, 2. porcelain containing alumina and 3 · eristobalite porcelain.

1. The feldspar porcelain is obtained by firing a mixture consisting essentially of 15 his 30% by weight quartz material, 20 to 40% by weight feldspar material and 40 to 60 wt.% clay material. The crystalline phase of this fired porcelain consists of 10 to 20 Wt% quartz and 10 to 20 wt% mullite, and the remainder consists of non-homogeneous glass. The raw material for this feldspar porcelain is relatively cheap and

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has excellent processability, so that it is suitable for porcelain electrical insulators has been used. However, it has the disadvantage that its mechanical strength is not very high, so that © s not for electrical Porcelain insulators can be used, which have to withstand high mechanical stress.

2 »The porcelain containing aluminum oxide was developed around. To improve the mechanical strength of the rock spar porcelain. The porcelain containing aluminum oxide is obtained by burning a mixture in which the quartz material partially or completely as well as part of the feldspar material and part of the clay material is replaced by 20 to 40 wt .-% aluminum oxide. The crystalline phase of this fired porcelain contains 20 to 40 weight percent alumina. The more aluminum oxide the porcelain contains, the greater its mechanical Strength.

Experiments have shown that the flexural strength of a glazed test sample made of porcelain containing aluminum oxide is of the order of 1200 to 1700 kg / cm. The aluminum oxide-containing porcelain has recently been widely used for porcelain electrical insulators, which have excellent mechanical properties Possess strength. However, the alumina-containing porcelain has the disadvantage that when designing a electrical porcelain insulator despite the excellent mechanical strength of the test sample a large safety factor must take into account for the following reasons? (a) If the diameter of the porcelain body increases, then the distribution of cracks and defects becomes greater, with the result that the homogeneity the material is lost; in other words, the mechanical strength decreases due to the size effect away. (b) The mechanical strength decreases when

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on the surface of the electrical porcelain insulator due to a rough treatment during transport and during manufacture. Scratches occur or if damage is caused by malicious intent on the surface of the electrical porcelain insulator, such as with a gunshot, etc. caused *

The Kristobalitporzellan is thereby obtained, that burns a mixture whose chemical composition is essentially the same as that of Feldspatporzellans. The crystalline phase of the fired Kristobalitporzellans contains not only fullite and quartz but also Kristbaiite crystals, which tend to axis strongly in a thermal treatment. The presence of the crystallite crystals makes the mechanical strength of undamaged Eristo "balitporaellan higher than that of feldspar porcelain". The mechanical strength of undamaged crystallite porcelain is lower than that of porcelain containing aluminum oxide, but the rate of decrease in the mechanical strength of undamaged Eristobalite porcelain is lower due to the size effect as hazy from the aluminum oxide-containing Poraellans. In addition, the flexural strength of externally damaged eristobalite porcelain is not sufficiently high to be able to withstand the particularly high flexural stresses that occur with electrical Porsiellan insulators ο

In DiS 1 281 9 ^ 7 a porcelain object is described, which consists essentially of 100 parts by weight of conventional porcelain and additionally of 3 to 15 parts by weight of mullite, 3 to 10 The weight of the crystal is composed of 3 to 10 weight of the aluminum oxide

With such a porcelain counter-star ... the maehaniache will be vrird Strength improved by the addition of the KuI] itε, the

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deformation occurring during firing due to the addition of mullite prevented by the addition of aluminum oxide, and the decrease in the temperature caused by the addition of mullite and aluminum oxide thermal expansion compensated by the addition τ on Kristobalii So can, so the mechanical strength of the above Porcelain object can be increased to a value which is above the uppermost limit of the mechanical strength of the usual. Porcelain lies »However, the mechanical strength this porcelain diminishes when the surface is external damaged

The object of the invention is to provide an electrical porcelain « insulator with improved mechanical strength imd to create a process for the production of the same "

The invention is based on the finding that an electrical! ⁴ Porcelain insulator with excellent flexural strength after external damage can be produced by producing a mixture consisting of 65 to 90% by weight of a mass 1 \ md 10 "to 35% by weight of a mass B, the mixture dehydrated and dried the body in a body ver * = · formed and ύοώ the dried body at a temperature. 1200-1 _o 350 ° 0 burns _s wherein the mass a essentially of Feldspatmaterial, .Quarsmateria] and audio material is, the mineralogical 10 to 20% by weight of feldspar, 30 to 60% by weight of ars and 20 to 50% by weight of clay, and chemically 65 "to S3% by weight =% SiO ₂ , 15 to 28% by weight of Al ₂ O ,, 2.0 to 4.5% by weight! 6 EgO + la 0 and unavoidable impurities, the ratio of EgO / CKgO -s- Ha ₂ O) being between 1s 10 and If2 and where the above The quartz material mentioned has such a grain size distribution that not more than 20 ßew.-9ä of the particles have an effective diameter of more than 10 A ', and xvorin the mass B.
consists"

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BATH ORIGINAL

The invention is explained in more detail in the following description, in which reference is also made to the accompanying drawings . .

See the drawings

FIG. 1 curves which explain the effect of the amount of crystallite on the flexural strength of porcelain test specimens; and

Figure 2 graphs which compare the flexural strength of electrical porcelain insulators according to the invention show with those of conventional electrical porcelain insulators-

First, however, a preferred manufacturing procedure is described of the porcelain insulators according to the invention specified »

First the masses A and B are produced »

The Hasse A consists essentially of feldspar material that contains more than 4-0% by weight of feldspar and quartz and possibly a smaller amount of sericite, of quartz material that contains more than 50% by weight of quartz, kaolinite and sericite and possibly a smaller amount Contains amount of feldspar, and also clay material that contains more than 80% by weight of kaolinite and a smaller amount of quartz and, if necessary, a smaller amount of feldspar, the mineralogically speaking 10 to 20% by weight of feldspar, 30 to 60% by weight. contains% quartz and 20 to 50% clay and chemically GeWo- seen 65-83 Qe \ u- SiO _2, 15 to 28 wt .-% Al ₃ O _5, 2.0 to 4.5 wt "-% K ₃ O + NapO and unavoidable impurities, the ratio of K ₂ 0 / (K ₂ 0 * ^Ka 2 ⁰ ^ ^between " ¹ ^ ⁰ ^ ³¹ * ³ - ^ ¹ - ² and the above-mentioned quartz material having such a grain size distribution, that no more than 20% by weight of the particles have an effective diameter of more than 10 / t nes pulveriaators, like ζ.Β »a drum, pulverized.

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The mass B consists of aluminum oxide material, i.e. powdered calcined aluminum oxide produced by the Bayer process, or powdered calcined bauxite, this bauxite being produced by raw bauxite having a loss on ignition of 11.0 to 33 * Has 0% by weight and from 0.5 "to 8.0% by weight SiO ₂ , 53.0 to 80.0% by weight Al ₂ O ₅ , 0.7 to 4.0% by weight % Fe ₂ O ,, 0.5 to 10.0% by weight ϊί ° 2 * not more than 1% by weight GaO, not more than 0.5% by weight MgO, not more than 1.0 Gevv .-% K ₃ O and not more than 1.0 Gav., -% ITa ₂ O, crushed, then pulverized the crushed product to a particle size on the order of less than 30 mm / the particles in an oven, such as in a rotary kiln, calcined at a temperature of 1 * 350 to 1 «600 ° C in order to remove water, crystallization water and organic substances, whereby calcined bauxite clinkers are obtained , for example by an edge mill, and finally by a pulverizer, such as ζ ^ B. a drum, pulverized.

65 to 90% by weight of mass A and 10 to 35% by weight of class B are mixed in a mixer such as a drum. The mixture produced in this way is dewatered and deformed into a body. The body is then dried, and the dried body is kept at a temperature Fired from 1,200 to 1,350 ° E around a porcelain body the crystalline phase of which consists of corundum, Kristobalit, Mulit and quartz and contains 25 to 40 wt .-% Kristobalit.

It was also established that to whom the fired porcelain body Contains 25 to 40% by weight of cisotbalite, the mechanical Strength of an externally damaged porcelain is considerably improved from the following Establish;

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1 shows characteristic curves of porcelain test bodies which were fired at 1,280 ⁰ C from mixtures & US 100 wt .-% of a mass and O wt.? "-"Aluminiumoxidmatei'ial, from 90 wt .-% of a mass and 10 percent by .-% Aluminiumüjcidmaterial bsw "of 75% Gewo- a mass and 25% Ge \\ _a ~ alumina material bestandaip wherein the mass of various types of quartz material to different grain

and size distributions was crushed / from different species Feldspa ^ materlal and clay material had been produced. In FIG. 1, the abscissa shows the amount of fired eristobalite, while the ordinate shows the flexural strength. .

The flexural strength of undamaged rod-shaped porsell test bodies, each 8Θ in diameter mm. and had a length of 800 mm, was carried out using a Method measured in which the center is loaded. The flexural strength of externally damaged porcelain test bodies was measured »after that! part of the porcelain test piece, to which the maximum tensile strength occurred in this process, with the help of a chisel up to was cut to a depth of about 2 mm =

The amount of eristoball was determined by quantitative X-ray diffraction analysis determined.

From Figure 1 it can be seen that the flexural strength of externally damaged porcelain bodies is approximately 50 % of the flexural strength of undamaged porcelain test bodies if the amount of Er-i3tobalite is more than 25%, but that it is reduced to less than 40 % of the undamaged porcelain test bodies is when the amount of crystals is not more than 25% by weight. It is therefore evident that the resistance of electrical porcelain insulators which are externally damaged becomes greater if the porcelain body contains more than 25% by weight of eristobalite. Figure 1 also indicates that the flexural strength increases with the increase in the amount of the alumina material

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s-ceigt; una aais the flexural strength of an externally damaged insulator whose aluminum oxide material content is 0% by weight is in the same order of magnitude as that of porcelain bodies containing 10% by weight and 25% by weight of aluminum oxide material when the amount of the kristobalite is less than 25 Qev .-% , with the result that the flexural strength of externally damaged insulators has a low absolute value.

It is therefore apparent that the amount of the alumina material more than 10 wt -%, and should be that the amount of Kristobalits after firing should not be less than 25 wt .-%..

As already mentioned, it is desirable

that the porcelain body contains a large amount of eristobalite. The maximum amount of sristobalite in PorseXlan bodies _T dib at 1o200 to 1o.350 ° C from mixtures fired and soft. «? consist of the masses A and B, but should not exceed 40% by weight. If the> Pozrellankönoer contains more than 40% by weight of Krdstobalite, then the feldspar decreases and the quartz increases, with the result that the vitrification temperature increases considerably.

The reason why the mass A consists essentially of feldspar material, quartz material and clay material is as follows. First of all, the quartz material is dissolved in the feldspar glass, whereby the crystal is re-crystallized. Unavoidable impurities in the quartz material do not have this function. Further, the Peldspatmaterial is required to produce feldspar glass, while unavoidable Vere impurities not required Feldspatmaterial are, "to produce such a feldspar glass Finally e3? Are the ^r jkmmate3? Ial, has that plastic character 3n, good processability of Porcelain body, while unavoidable impurities in the clay do not have such a function »

The reason why the mineral composition of the mass A is based on

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- y -

10 to 20 wt% feldspar, 30 to 60 wt% quartz and 20 is limited to 50 wt% clay is the following. The above limitation makes it possible to use the method of the present invention for manufacturing electrical porcelain insulators practical to realize to electrical porcelain insulators with stable properties and with constant Producing quality The result is that the fired porcelain body is 25 to 40% by weight Contains Kristobalite.

The reason why the composition A chemically consists of 65 "to 83 wt .-% SiO ₂ , 15 to 28 wt .-% Al ₃ O ₃ , 2.0 to 4.5 wt .-% KgO + Na ₂ O and unavoidable impurities is why the ratio of K ₂ 0 / (K ₂ 0 + BTa ₂ O) is between 1s 10 and 1: 2 and why the quartz material has such a particle size distribution that not more than 20 wt .- ^ of the particles one having effective diameters of greater than 10 fi *, the following. the present after firing Kristobalitmenge depends on the amount of SiO _2, the amount of K ₀ O + Na ₀ O and the ratio of K _o 0 / (K _o 0 + Ka ₀ O)

^ ebild6F $ en ddd

which are in the / glass phase when the porcelain body is fired at the highest temperature. Smaller amounts of SiO ₂ , larger amounts of K ₂ O f E ^a p ° ^{and β3 η a} larger ratio of K ₂ 0 / (K ₂ 0 + Na ₂ O) cause a smaller amount of crystallite to crystallize out. According to the invention, a mixture containing 10 to 35 wt. It is necessary that the amount of SiO _{2 is} more than 65% by weight, the specified grain size distribution of the quartz material being maintained, so that the amount of K ₂ O + Na ₂ O is less than 4.5% by weight and that the ratio of K ₂ 0 / (K ₂ 0 + Na ₂ O) is less than 1: 2. In contrast, more than 83% by weight SiO ₂ and less than 2% by weight K2O + Na ₂ O or a ratio of K ₂ 0 / (K ₂ 0 + Na ₂ O) less than 1:10 results in an increase the glazing temperature, which makes it impossible in practice

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is to cause complete sintering to provide a porcelain electric insulator having a large diameter and to manufacture with a solid core.

The reason why the amount of the AlpO in which Hasse A is limited to / "5 to 28 Ge \. % Is as follows. When the SiO _{2 is} 65 to 83% by weight, the K ₂ ^{0 + Ha} 2 ° ² ° ^to 4.5% by weight and the ratio of K ₂ 0 / (E ₂ 0 + Na ₂ O) 1:10 to 1: 2, then the amount of Al ₂ O ^ falls naturally in a range from 15 to 28% by weight.

The reason why the grain size distribution of the quartz material is limited to not more than 20% by weight of particles having an effective diameter of more than 1 ^ is as follows. This restriction ensures an increase in the Si0 ₂ component, which dissolves in the glass phase during firing, so that more than 25% by weight crystallize.

The reason why the alumina mass B material is on 10 to 35% by weight is as follows. The more Alumina material is present in the mixture from which the porcelain body is fired, the higher the mechanical Strength of the insulator. On the other hand, more than 35 wt% alumina material makes higher firing temperature necessary for sintering the porcelain body, while less than 10% by weight of aluminum oxide material reduces the mechanical Result in strength of the insulator, so that the objects of the present invention are not achieved "

The reason why the firing temperature is limited to 1 »200-1350 ⁰ C, is as follows. When the porcelain body is fired at a temperature below 1,200 ⁰ C, then while if the porcelain body at temperatures of more than 1.35O ° C is fired, the glazing of ceramic body is incomplete, the porcelain body shows an unfavorable tendency to decrease in mechanical strength "

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mm » YY on

The crystalline phase of the fired porcelain body according to the invention contains quartz, mullite, Kristobalit and Korundum, and the presence of 25 to 4-0 wt .-% Kristobalit in the porcelain body considerably improves the mechanical strength of externally damaged electrical porcelain insulators · The corundum comes from the aluminum oxide material and improves the mechanical strength of the insulatorThe quartz and the mullite are porcelain, so that their presence in the fired porcelain body is unavoidable.

Calcined alumina or calcined bauxite available on the market can be used as the alumina material be used. The use of calcined bauxite results in a lower vitrification temperature Porcelain body than the use of calcined alumina available on the market, and there is also the advantage that an electric porcelain body with a mass iren core, which has a large diameter, can be produced comparatively easily »

The invention will now be explained in more detail with reference to the following examples. In each of the following examples, materials were used, their chemical composition and their mineralogical composition, which is determined by X-ray diffraction measured are given in Table 1 below.

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Tabel

Older bauxite available from the Harkt * calciner

Alumina

Ghenii

Giüh fyerlust ί SiO? ~ "

eetztaag

ISaaQa.

Mnsra-

! CaO

Total

Serigit

| Weight .- # ^ © idspatj

0.18

track

_QjlO2

track

0 ₅ 02

0.24

from Demerara

"Fukuahima Quartzite"

0.30

4.20

91.2 = 5

2

0.14

9937

0.20

0.04

track

Pottery stone "

"Euma! Noto- |" Hagasaki-

2.96

Peldspar "

0 _s 67

"Hiigata Feldspar"

0.39

0.75

■ 0.15

0.57

0.07

3.08

0.21

0.02

track

0.18

track

10.99

5? 66

99.84

.100.09

100.05

100.0

60.8

0.5

38.1

46.0

3 ₅ 60

9.8

89.7

"Gifu-

Gaerome

Volume"

12.64

0.63

0.06

0 _s 78

0.13

99.81 j 100.11

8.3

87.1

example 1

A porcelain was produced with the type shown in Table 2 below specified composition is used.

Table 2

Composition (wt .-%) conventional aluminum »
oxide-containing porcelain invention
according to
zallan O IA
CVJ CVJ Alumina '
Fukushima quartzite 20th
20th - Nagasaki feldspar 25th 1? Niigata feldspar - 38 Gifu gaerome clay 35 100 All in all 100

The Fukushima quartzite was previously pulverized so that 15% by weight of the particles had an effective diameter greater than 10 Å.

The final mixture produced was pulverized such that 18% by weight of the particles had an effective diameter of have more than 10 / ^.

The mixture having the composition shown in Table 2 was processed into a rod-shaped solid test body having a diameter of 120 mm. The test body was ^{fired at 1,300 °} C., a porcelain being obtained which had the properties given in Table 3 below. The amount of im burned

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~ 14

Kristobalite present in test specimens was determined by means of X-ray diffraction determined quantitatively. The average strength values of undamaged and damaged solids were measured by the same method described above.

Table 3

according to the invention
porcelain conventional
porcelain Amount of Kristobalite,
Wt% 29.4 0 Flexural strength of un
damaged porcelain 134-0 kg / cm ² 1150 kg / cm ^ Flexural strength of
externally damaged
tem porcelain (2 mm
deep) £ "2 ρ
700 kg / cm 540 kg / cm ² ^ 2Ai χ 100 (%) 52.2 29.6

Example 2

25% by weight of calcined bauxite, which was used as an alumina material and which was pulverized so that 30 % of the particles had an effective diameter greater than 10 H- ; 22% by weight of Kumamoto pottery stone, which was pulverized so that 18% by weight of the particles had an effective diameter of more than 10 Λ, 23% by weight of Nagasaki feldspar and 30% by weight of Gifu-Gaerome clay were mixed together. The mixture thus obtained was further pulverized so that 20% by weight of the particles had an effective diameter greater than 10 ° C. It became an overhead line insulator with a massive

Core produced, the fired dimensions of which were as follows: cylinder diameter 125 mm, disk diameter 220 mm and total length II50 mm. This test insulator was fired at 1280 ⁰ C. The amount of crystallite present in the fired test insulator is 34.8% by weight (determined by quantitative X-ray diffraction analysis). The average value of the flexural strength ϋ'Λ of the undamaged free

line insulator was 1,280 kg / cm. The average flexural strength 6 ^ 2 value of the test insulator when the three disks were hammered off in the vicinity of the portion subjected to the maximum tensile stress was 660 kg / cm. The value ^ χ 100 was thus y \, 5% · In contrast, a conventional crystallite porcelain electric insulator, which did not contain an alumina material, showed the following values; & Λ «860 kg / cm,

- 410 kg / cm ² and £ * 2/6 * '1 χ 100 % 4? , 6%. A conventional electric alumina-porcelain insulator, the alumina material content was 25 "Addicted ™ ^, showed the following value $ ^J i * 1.200 kg / cm ^2, ^ 2 ■ · * 420 kg / cm ² and Γ2 / ^ 1 χ 100 The above results are shown in FIG.

The electrical porcelain insulators according to the invention, which have excellent mechanical strength and excellent Have flexural strength after an external damage, represent a considerable improvement of the previous high-strength electrical porcelain insulators for High voltage and ultra high voltage lines. One their main advantages lie in the improved strength properties, which makes a significant contribution in the field which brings with it high voltage lines.

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Claims (10)

- 16 claims Electrical porcelain insulator with excellent mechanical strength and excellent flexural strength after external damage, characterized in that the crystalline phase of the porcelain body consists of corundum, Mullite, quartz and Kristobalit and that the porcelain body Contains 25 to 40 wt .-% Kristobalit. 2. Insulator according to claim 1, characterized in that it is fired from a mixture that consists of 65 to 90% by weight of a mass A and 10 to 35% by weight of a mass B, the crystalline phase of the porcelain body Corundum, Hallit, quartz and Kristobalit and the porcelain body contains 25 to 40 wt .-% Kristobalit, in which the mass A consists essentially of feldspar material, quartz material and clay material, which from a mineralogical point of view consists of 10 to 20 wt .-% feldspar, 30 to 60% by weight quartz and 20 to 50% by weight clay and which, from a chemical point of view, consist of 65 to 83% by weight SiOg, 15 to 28% by weight Al ₂ O, 2.0 to 4 , 5% by weight K ₂ O + Ia ₂ O and unavoidable impurities, the ratio of K ₂ O / (K ₂ O + Ha ₂ O) being between 1s10 and 1s2 and the quartz material having a grain size distribution such that no more than 20% by weight of particles with an effective diameter greater than 10 / & are present and where rin the mass B consists of an aluminum oxide material ". 3 " insulator according to claim 1 or 2" characterized in that the aluminum oxide material consists of calcined bauxite " 4. Insulator according to claim 1 © of 2, characterized in that the aluminum oxide material consists of calcined aluminum oxide consists" 5 · Insulator according to one of the preceding claims, characterized in that it has a solid core " 6. Process for producing an insulator according to one of the preceding claims, characterized in that a mixture is produced which consists of 65 to 90% by weight of a mass A and 10 to 35% by weight of a mass B, the mixture dehydrated and deformed into a body, the body dries and the dried body burns at a temperature of 1,200 to 1,350 ° 0, wherein the mass A consists essentially of feldspar material, quartz material and clay material, which in mineralogical terms consists of 10 to 20 wt. -% feldspar, 30 to 60% by weight quartz and 20 to 50% by weight clay and which, in chemical terms, is composed of 65 to 83% by weight SiO ₂ , 15 to 28% by weight Al ₂ O, , 2.0 to 4.5% by weight K ₂ O + Ha ₂ O and unavoidable impurities and has a ratio of K ₂ 0 / (K ₂ 0 + Ha ₂ O) of 1s10 to 1: 2, the Quartz material has a grain size distribution such that no more than 20% by weight of particles with an effective diameter vo n is more than 10 r * , and wherein the Itasse B is made of an alumina material. 7. The method according to claim 6, characterized in that calcined bauxite is used as the aluminum oxide material. 8. The method according to claim 6, characterized in that calcified aluminum oxide is used as the aluminum oxide material will. 9 · Method according to one of claims 6 to 8, characterized characterized in that one produces a body with a solid core. 10.9810 / 1601